Firearms are used in a variety of ways, including hunting and sporting activities, law enforcement activities and military activities. In hunting activities, spent bullets or parts of spent bullets remain in the environment. They may be eaten by game, or other animals or birds, either inadvertently or out of curiosity. This can cause poisoning effects, depending on the type of bullet. If the bullets contain lead, poisoning and environmental effects pose significant concerns about health issues, and have resulted in governmental regulations concerning the banning of the use of lead in bullets. In sporting activities and testing of bullets at a firing range, fumes from lead bullets pose a significant health issue.
Lead-free bullets are known. For instance, U.S. Pat. No. 5,399,187 discloses a bullet formed from tungsten, or an alloy of tungsten, and phenol formaldehyde or polymethylmethacrylate polymers, U.S. Pat. No. 5,012,743 discloses a light weight elongated projectile formed from a casing of copper alloy, steel or similar material and a lower density core e.g. polycarbonate or polyamide. WO 95/23952 discloses a projectile having a core of polyethylene and iron. Projectiles formed from bismuth alloys are disclosed in WO 92/08097 and WO 95/08748.
Lead-free bullets that are particularly intended to retain markings of the barrel of the firearm after the bullet is fired are disclosed in U.S. patent application Ser. No. 09/101,844, filed Oct. 5, 1998 of A. J. Cesaroni. Such bullets have a core formed from a lead-free composition of a filler and an amorphous or low crystallinity polymer e.g. ethylene/methacrylic acid copolymer ionomers, polyetherester elastomers and polyamides. Examples of the filler include copper, tungsten, bismuth, tin and stainless steel. In embodiments, the shell or casing of the bullet may be a truncated cone or truncated parabellum, and the tip may be parabolic, rounded or hollow point.
Lead-free projectiles that are currently being manufactured have, for 0.223 calibre, a maximum weight of about 50 grains. Higher weights for the same calibre would have greater impact during use.
Examples of lead-free projectiles are being manufactured from powdered metals using a sintering process. However, such projectiles do not give the desired results when penetrating tissue. The projectile tends to remain intact and consequently induces minimal trauma when penetrating tissue. Moreover, the projectile will ricochet if it hits a hard object, scattering projectile materials and potentially injuring innocent persons, including the shooter. In addition, the manufacturing process typically includes a step of crimping the projectile into a brass casing, and that step may lead to fracture of the projectile.
A lead-free projectile that could be manufactured with a higher weight, and a manufacturing process that is not susceptible to the above defects of manufacture would be useful.